Can IIRF Match against POST variables?

Hi we are being attacked by Arabian hackers and I thought I could use IIRF to block the attacks, I can do the GET rewrites but the attack can also come VIA a POST request, is there anyway to match against POST form content/variables?

I can't see anything in the Server Variable References so I am guessing it's avoided due to form content size or ISAPI restrictions, but it would be good to know!

I think I could do this with mod_security on apache, I wonder if there's an IIS ISAPI port....